If the BOE doesn’t raise its key interest rate, the big question is whether it will continue to indicate that a series of increases will be needed to tame inflation

LONDON—When the BOE last published forecasts for growth and inflation in February, Gov. Mark Carney said the key interest rate would have to rise “somewhat earlier and to a somewhat great extent than we had thought.” Investors immediately looked to May 10 for liftoff, holding to that belief until mid-April, when a combination of fresh guidance from Mr. Carney and a series of very weak economic data releases changed the opinion of most BOE watchers, who now expect the key rate to remain at the crisis-era setting of 0.5%. Assuming they prove to be right, the big question is whether the BOE views a poor first quarter as...